Microphone-transmitter.



J. E, B. HOLLADAY. MICROPHONE TRANSMITTER. APPLICATION FILED JUNE'H, 1916;

1,246,429. Patented Nov. 13, 1917 UNITED STATES PATENT OFFICE.

JOSEPH E. B. HOLLADAY, OF SUFFOLK, VIRGINIA, ASSIGNOR TO THE HOLLADA Y DETEGTO COMPANY, INC., OF SUFFOLK, VIRGINIA, A CORPORATION OF VIRGINIA.

MICROPHONE-TRANSMITTER.

Specification of Letters Patent.-

Patented Nov. 13, 1917..

Application filed June 17, 1916. Serial No. 104,213.

To all whom it may concern Be it known that I, JOSEPH E. B. HOLLA- DAY, a citizen of the United States, residing at Suflolk, in the county of Nansemond and 6 State of Virginia, have invented certain new and useful Improvements in Microphone- Transmitters, of which the following is a specification. I

This invention relates to microphone transmitters, a type particularly adapted for use in combination with a sensitive receiver for the purpose of greatly amplifying the sensitiveness of the instruments, whereby any slight sound or vibration may be detected at the receiving end.

In the accompanying drawings, Figure 1, is a plan view of the instrument with the cover removed; Fig. 2 is an enlarged sectional View taken' on line 2-2 of Fig. 1.

Fig. 3 is a rear view; and

Fig. 4, shows various elements which go to make up the transmitter, (excepting the granular carbon) showing said parts in the relative positions they assume when assemble The numeral 1, indicates a casing or back exteriorly threaded at its open end as at 2. A circular cap or face plate 3 perforated at 80 its center is provided upon its interior with threads 4-, which threads are adapted to be received by the threaded portion 2 of the base plate.

. An annular metal ring 5 is received with- 85 in the wall portions of the base 1, being of a sufficient diameter and thickness to be frictionally held therein; the upper surfaces of said ring and wall portions being flush with each other. An insulating disk 6 is secured to the back 1, being of a sufiicient diameter to be snugly received withinthe inner diameter of the metal ring 5. Mounted upon this insulating disk is a metal disk 7 which is secured to the back 1 by suitable fastening 46 screws 8, 9 and 10. The screws 8 and 10 are surrounded by suitable insulating bushings 11, which serve to insulate the screws from the metal disk 7.

A terminal 12 is secured to screw 8, which, as disclosed in Fig. 1, completes a metallic circuit between one side of the circuit to the metal casing 1, while the screw 9, as shown in Fig. 2, is adapted to secure a terminal 13 direct to the disk 7. Mounted upon I the metal disk 7 is a circular carbon block 14 hemisphericalcavities 16having highly 01- ished faces, and being partly filled Wit a conducting medium 17, in the present instance, granular carbon. More or less of these granular carbons are used according to the length of wires used, or rather accord-' I ing to the increased or decreased resistance.

An insulating mica ring 18 is received upon the outer face of the metal ring 5 and wall portions of the back 1, upon which is adapted to rest a carbon diaphragm 19. The relative position of said carbon block 14 with respect to said diaphragm 19 is such' that while the said block does not actually contact the said diaphragm, yet they are so intimate that the carbon granules contained in said cavities will not escape, and are held therein by said diaphragm.

Resting upon the carbon diaphragm 19 is a card board washer 20, which forms an insulated core for a wire coil 21. '80

It will be noted in Fig. 2, the diameter of the carbon diaphragm is slightly less than the inside diameter. of the cap 3, while the diameter of the said coil is practically the same as the diameter of the said cap, thereby 86 forming an electrical connection between the two, which coil in turn transmits current to the said carbon diaphragm 19.

Thus it will bc'seen that a transmitter constructed as abog, described is capable of 90 high eiiiciency prif {icipally by the introduction of the wire coil directly above the carbon diaphragm 19, which coilserves as the electrical conductor between the carbon diaphragm and the finetallic cap 3. which in turn is in contact with the backplate 1, which is connected to the opposite side of the line from that of the carbon block 14.

I claim:

1. In a transmitter, thecombination of an electrode, a diaphra electrdde arranged across the face of said electrode, and a coil arranged, upon the outer faceof the said diaphragm and in electrical connection therewith. 106

2. In a transmitter, the combination of a, back plate, a metal disk conn'ectedto but. insulated therefrom, fan electrodef'connected thereto, a diaphragrn'electrode arranged across the face mason annulare lectrical 110' coil arranged upon the outer face of the said diaphragm electrode and in electrical connection therewith, and a perforated cap or face plate adapted to surround said diaphragm electrode and coil for securing them in place, said face plate and back plate being detachably secured together.

3. In a transmitter the combination of a back plate, an annular ring arranged Within the Wall portions of said back plate, a metal disk connected to but insulated from said back plate, a carbon block elect-rode provided with pockets, carbon granules arranged Within the said pockets, a diaphragm electrode received upon but insulated from said annular ring. and arranged across the face of said carbon block electrode, an annular electrical coil arranged upon the outer face of the diaphragm electrode, and a perforated cap or face plate, adapted to surround said carbon diaphragm or coil for securing them in place, said face plate and back plate being detachably secured t0- gether.

4. In a transmitter, the combination of a carbon block electrode provided with pockets, carbon granules arranged Within said pockets, a carbon diaphragm electrode arranged across the faceof said carbon block electrode, spaced apart therefrom, and in contact with said carbon granules, and a coil arranged upon the outer face of the said carbon diaphragm and in electrical connection therewith.

A transmitter, comprising oppositely disposed electrodes and an annular coil arranged upon one of the electrodes and in electrical connection. therewith.

'In testimonv whereof I afiix my signature.

' JOSEPH E. B. HOL LADAY. 

